1. Field of the Invention
This invention relates to a device for the location and catheterization of the surroundings of a nerve of a human or animal body as well as with a method for the location and catheterization of such a surroundings of a nerve.
2. Description of Prior Art
In surgical processes on the upper and lower extremities, as well as in replantation surgery and pain therapy of a patient, it may be expedient to produce a longer-lasting or continuous blockage of the nerve in the affected area of the human or animal body as well as to maintain this blockade in long-term therapy over a long period of time.
According to conventional methods, a relatively large amount of a local anesthetic for blocking the nerve is required, but this increases the risk of side effects for the patient.
In order to reduce the necessary amount of local anesthetic and its side effects, it is therefore desirable to apply the local anesthetic as close as possible to the surroundings of the nerve to be blocked, so that the desired blocking action of the local anesthetic proceeds satisfactorily, even when a small amount is used. This can be achieved by injection of the local anesthetic directly into the closest surroundings of the nerve to be blocked.
According to the invention, "surroundings of a nerve" is understood to mean optimally the region which is at the smallest possible distance around the nerve to be blocked, but where actual contact with the nerve is excluded.
In this connection, it is known that an electrically conducting metallic needle, which is connected to an electrical voltage source, can be used to locate and search for the nerve to be blocked, in which case the metallic needle is under voltage and serves as an electrode. Using a reference electrode, a stimulating current is given off which is transferred to the nerve to be located and which can be measured by the inserted needle, so that the treating physician is able to locate precisely the nerve to be blocked with the aid of this stimulating current and can guide the needle as close to the nerve as possible, in order to obtain optimum use of the local anesthetic at the nerve, in order to block it.
As soon as the metallic needle serving as an electrode penetrates to the neighborhood of the nerve to be located, a circuit is closed and the nerve is stimulated, which is manifested, for example, in externally visible muscular contractions of the patient.
U.S. Pat. No. 3,682,162 teaches a needle consisting of two concentrically arranged electrodes electrically insulated from one another, which can be connected to an external voltage source and with which the nerve to be located and blocked can be located with the aid of the stimulating current technique described above. A through-hole, arranged in a central area of the central axis of the concentrically arranged electrodes can then be used to introduce a local anesthetic after reaching the immediate surroundings of the desired nerve and applied to it. The known needle has a connection for this purpose at its proximal end, where the syringe, which is known, with the local anesthetic, can be set and then this can be released through the distal end inserted into the immediate surroundings of the nerve.
Especially for providing longer-lasting or continuous nerve blockage as well as for safe long-term therapy, it is necessary to provide a local anesthetic periodically or continuously to the nerve over a long period of time, and, for this, usually a finer catheter is placed all the way to the corresponding immediate surroundings of the nerve to be blocked, but without contacting the nerve mechanically.
For example, it is known from European Patent Publication EP 0102538 that one can first locate the nerve to be blocked with an electrically conducting puncture needle in the manner already described above. Through this puncture needle, the first dose of local anesthetic can be injected through its distal end into the surroundings of the nerve by connecting a syringe at the proximal end (called Single-shot). Therefore, through the puncture needle, a self-retaining canula is pushed into the surroundings of the located nerve to be blocked, the metallic puncture needle serving as guide for the self-retained canula. The puncture needle can be withdrawn from the body while the self-retaining canula remains fixed and lies with its distal end in the surroundings of the nerve to be blocked. Then, it is possible to push a long guide wire through the self-retaining canula into the surroundings of the nerve to be blocked. The self-retaining canula can be removed, having the guide wire remaining in position, and finally the catheter can be pushed forward through the guide wire all the way to the surroundings of the nerve. After removal of the guide wire, the catheter is placed in the surroundings of the nerve to be blocked and serves for the continuous or periodic provision of local anesthetic to the nerve to be blocked.
However, a disadvantage of this known device is, first of all, the complicated structure of the device having a number of individual parts, namely, puncture needle, self-retaining canula, guide wire and catheter, which require highly skilled maneuvering by the operating physician and make the handling unnecessarily difficult. Another problem is that the self-retaining canula to be positioned is usually made of a flexible plastic and, after the metallic puncture needle is removed, it no longer receives guidance, so that unintended movements of the patient could cause a change in the position of the self-retaining canula and then the guide wire, as well as the catheter introduced over it will no longer be in the precise position located with the metallic puncture needle in the surroundings of the nerve to be blocked. This problem increases with increasing depth of the position of the nerve to be blocked within the body, because, with increasing length of introduction or depth of the self-retaining canula, the risk of unintended change of the located position increases. Therefore, the device of the art is suitable for producing blockage of the nerve only in a limited area of application, namely just close to the skin surface, such as in the area of the arm. However this undesirably limits the area of application.